The CTGF polypeptides are structurally and functionally related to a family of growth factors which include IGF (insulin-like growth factor), PDGF (platelet-derived growth factor), and FGF (fibroblast growth factor). This emerging family of secreted proteins are a group of cysteine-rich proteins. This group of growth factors are important for normal growth, differentiation, morphogenesis of the cartilaginous skeleton of an embryo and cell growth. Among some of the functions that have been discovered for these growth factors are wound healing, tissue repair, implant fixation and stimulating increased bone mass.
The extended superfamily of growth factors include TGF (transforming growth factor), bone morphogenic factors, and activins, among others.
The most well-known growth factor, TGF exerts a number of different effects on a variety of cells. For example, TGF-alpha can inhibit the differentiation of certain cells of mesodermal origin (Florini, J. R. et al., J. Biol. Chem., 261:1659-16513 (1986) induced the differentiation of others (Seyedine, S. M. et al., PNAS USA, 82:2267-2271 (1987) and potently inhibit proliferation of various types of epithelial cells, (Tucker, R. F., Science, 226:705-705 (1984)). This last activity has led to the speculation that one important physiological role for TGF-″ is to maintain the repressed growth state of many types of cells. Accordingly, cells that lose the ability to respond to TGF-″ are more likely to exhibit uncontrolled growth and become tumorigenic.
Accordingly, due to amino acid sequence homology the polypeptide of the present invention is a member of this extended family of growth factors which has many effects on a variety of different tissues.